Quaternary deposits of the Fuegian Atlantic coast between Peñas and Ewan capes

Abstract

The littoral zone of north-eastern Tierra del Fuego located between Cabo Peñas and Cabo Ewan was affected by processes related to the Quaternary glaciations and marine transgressions. This was a free-ice area at least since 1.5 Ma B.P. Glacifluvial deposits were re-worked by litoral processes that formed gravel beaches during highstands of the sea level. Four levels of Pleistocene gravel beaches were recognized in the area. The younger and lower levels would probably correspond to the oxygen isotope stage 5e (La Sara Formation, altitude about 7 m above the present storm berm) and 7 (Shaiwaal Formation, 12 m a.p.s.b.). The older and higher levels would be older than the isotope stage 18O 11 (Viamonte Formation, 38 m a.p.s.b. and Najmishk Formation, 53 m a.p.s.b.). These are the southernmost Pleistocene raised beaches of the world. During the Holocene, approximately 5000 yr B.P., beach ridge plains composed of gravel begun to plug the inner estuaries of the Ensenada de la Colonia and Río Fuego palaeoembayments. These beach ridge plains have shown a regressive behaviour during the Holocene. They do not revealed erosion, sediment recycling at the seaward flank (cannibalism), and a significant landward retreat like the northernmost littoral environments of the Atlantic coast of Tierra del Fuego.